I found this video which seems to animate the concept nicely:

https://www.youtube.com/watch?v=udffed4Pq3g

Bloody Hell I did not know that. I have parts of broken Katadyn PUR-06. I was thinking of rebuilding it from better materials. The pressure recovery is the worst part. I can totally fathom now a hand-held desalinator with only rotating parts running from solar or Li-On batteries.

PUR-06 lasts 300 days, not "indefinitely": https://youtu.be/dNjdgfGgPdE?t=208

I don't know how well this would scale down. Viscosity would work against you.

Thank you, that was fascinating.

Awesome video. One of the better uses of Youtube, and what we should be striving for in terms of "online content".

Awesome. The video made it crystal clear.

That is such an incredibly smart piece of design. A tip of the hat to whom ever thought it up.

Leif J. Hauge

https://www.powershow.com/download/3b604b-ZGQwN/Pressure_Exc...

Read the history, including how the then-current prototype (out of series of improved versions developed over the 12 years it took to get to a market ready design) and all the inventor's personal belongings were lost in the invasion of Kuwait.

So they took the technology of the revolver and applied it to pressure relief. Fascinating stuff.

>One particularly efficient type of pressure exchanger is a rotary pressure exchanger. This device uses a cylindrical rotor with longitudinal ducts parallel to its rotational axis. The rotor spins inside a sleeve between two end covers. Pressure energy is transferred directly from the high pressure stream to the low pressure stream in the ducts of the rotor. Some fluid that remains in the ducts serves as a barrier that inhibits mixing between the streams. This rotational action is similar to that of an old fashioned machine gun firing high pressure bullets and it is continuously refilled with new fluid cartridges. The ducts of the rotor charge and discharge as the pressure transfer process repeats itself.

Thanks for pointing this out. I knew that recovering pressure from the outgoing brine was an important efficiency measure but I assumed it was done using a hydraulic motor coupled directly to a pump arrangement.

very similar in principle to 10 years younger https://en.wikipedia.org/wiki/Pressure_wave_supercharger

That sounds like it would be a great way to eliminate the EGR system on vehicles as well if there was a way to vary the relative speed of the rotor to the crankshaft.